1. Field of the Invention
This invention relates to asphalt having a high adhesion strength and its preparation. Particularly, it relates to a novel asphalt additive for imparting to asphalt a high adhesion strength when the additive is incorporated in asphalt in a small amount.
2. Description of the Prior Art
It is known that, in case asphalt is used for pavement, it is necessary to attain a sufficient adhesion between an aggregate such as crushed stone or sand and asphalt.
However, since the surface of such aggregate to which asphalt is applied is generally hydrophilic, if it is wet with water, it is difficult to stick asphalt to such aggregate. Further, even if asphalt is once coated to the aggregate, it is stripped off by an action of rain water, underground water and water contained in the aggregate per se. This is the defect of asphalt as regards its general properties.
In asphalt-paved roads, as the degree of the stripping of asphalt is advanced, necessity of repair works such as overlaying is increased, resulting in apparent economical disadvantages. Thus, occurrence of stripping of asphalt gives great influences to the durability of paved roads.
Diamines and imidazoline compounds have heretofore been mainly used as antistripping agents or adhesion agents for improving the adhesion property of asphalt.
However, these compounds fail to impart a practically sufficient adhesive strength. More specifically, the period during which the effect of these compounds is sustainable is generally about 3 years when they are used in amounts of 2.0% by weight based on asphalt.